Research Centre for Medical Genetics

Leber’s hereditary optic neuropathy (LHON) is a mitochondrial disorder characterized by central vision loss, primarily resulting from mutations disrupting the electron transport chain. The most prevalent LHON-causing mutation is mt.11778G>A in the mitochondrial MT-ND4 gene, which encodes a critical subunit of complex I. Allotopic expression, a promising gene therapy strategy, aims to deliver a functional nuclear version of ND4 into the cell nucleus and target the resulting protein to the mitochondria. The efficiency of this approach critically depends on the mitochondrial targeting signal used. In this study, we screened five different MTS sequences to optimize the allotopic expression of ND4 in a HEK-293 cellular model of LHON harboring the mt.11778G>A mutation. We identified MTS-cox8k as the most effective signal for restoring mitochondrial function. Treatment with this construct significantly mitigated key pathological hallmarks: reactive oxygen species decreased by 72%, mitochondrial calcium levels dropped by 47%, and mitochondrial membrane potential (ΔΨm) increased by 38%. These results underscore the therapeutic potential of allotopic ND4 expression and highlight the critical importance of MTS optimization for developing effective treatments for mitochondrial diseases like LHON.

Actinopathies are myopathies associated with pathogenic variants in ACTA1, a gene encoding the skeletal alpha-actin protein. Although patients most frequently have a severe congenital myopathy, an important clinical and myopathological variability has been described. Recently, a scapuloperoneal myopathy phenotype associated with ACTA1 has been reported. Here, we present a Russian woman with a late-onset, slowly progressive, scapuloperoneal actinopathy associated with an unpublished heterozygous pathogenic ACTA1 variant. We performed a thorough analysis of clinical, muscle imaging, muscle biopsy, genetic, protein and cardiac alpha-actin expression data from a 65-year-old woman with a scapuloperoneal myopathy phenotype. Disease onset was at around 30 years with proximal lower limbs muscle weakness, which slowly progressed towards an upper and lower limb distal involvement with prominent weakness of the fourth and fifth finger extensors. A muscle MRI showed a symmetric axial involvement, while lower limbs sections evidenced a severe symmetric involvement of quadriceps and biceps femoris long head, and a symmetric involvement of medial gastrocnemius associated with a right tibialis anterior involvement. Muscle biopsy showed cores and rods. The patient harboured the unpublished NM_001100.4:c.1001C > T, p.(Pro334Leu) ACTA1 variant. Immunofluorescence and western blot studies showed an increased expression of cardiac alpha-actin, an actin isoform which is normally predominant in the prenatal skeletal muscles and adult heart muscle, suggesting a possible role of this isoform in milder actinopathy phenotypes. We report a milder, late-onset, slowly progressive scapuloperoneal myopathy phenotype with cores and rods and cardiac alpha-actin overexpression, thus expanding the spectrum of actinopathies.

Introduction. Despite favorable prognosis for differentiated thyroid cancer, 5–10 % of the cases are radioiodine-refractory form of this pathology characterized by aggressive course. Molecular and genetic causes of the resistance are genetic mutations, primarily in the BRAF (V600E mutations), TP53, TERT, RAS, NTRK and RET genes, oligoclonality, and somatic tumor heterogeneity. These cell events can affect response to targeted therapy, promote the «evasion» effect, development of radioiodine resistance, and underlie the possibility of tumor re-differentiation when treatment affects these targets. Clinical case. The article describes a clinical case of combination treatment of differentiated thyroid cancer with lung metastases. In 2016–2022, the female patient received 3 courses of radioiodine therapy which did not achieve any significant effect. Due to this, targeted therapy with sorafenib at the place of residence was initiated. Considering development of medication intolerance and disease progression (local metastasis of BRAF-positive tumor and laryngeal stenosis), targeted therapy was switched to BRAF / MEK-specific with subsequent course of radioiodine therapy and achievement of stable disease for 1 year. Genetic examination of the primary tumor and metastasis showed presence of the BRAFV600E mutation. Variant allele frequencies (VAF) in metastasis and recurrent tumor were 12 and 6 %, respectively. In the recurrent tumor, H1047L mutation in the PIK3CA gene was found (VAF 8 %). Previous examinations in two other laboratories did not show BRAF gene mutation in this tumor which did not correspond to primary partial response to targeted therapy with BRAF / MEK inhibitors. That said, our analysis identified this mutation. Conclusion. The obtained data highlight significant diagnostic difficulties of analysis of formalin-fixed and paraffin-embedded samples: preanalytical degradation of nucleic acids, fixation artefacts, low VAF, non-representative biopsy sampling increase the risk of false negative results. The presented clinical case demonstrates the necessity of routing of patients with aggressive tumors into specialized centers, and that treatment and diagnostic tactics should be determined by a qualified multidisciplinary team.

Patients with asthma are at increased risk of developing osteopenia due to decreased bone mineral density (BMD). Particular attention is given to the role of vitamin D, whose deficiency is associated with the management of symptoms and bone health. Study Objective. To study BMD and its biochemical markers, with an emphasis on vitamin D status and intake in children with asthma in the Moscow region. Materials and Methods. Anamnestic, questionnaire, and laboratory methods were used, including assessment of nutritional impact, grade D, biochemical markers of bone metabolism, and molecular genetic analysis. Mineral support was obtained using X-ray densitometry. Data were statistically processed using SPSS Statistics 26 (IBM) using parametric and nonparametric me­ thods at a significance level of p <0.05. Results. The included study included 100 children with asthma, 15 % of whom had AD, and showed decreased BMD of varying severity. Most patients had low vitamin D levels, which were gradually adjusted and required oral cholecalciferol. High-dose inhaled glucocorticosteroids were associated with a more frequent decrease in BMD, while higher BMD values were recorded in children with moderate physical activity. The level of 25(OH)D was significantly lower in patients with asthma carrying the GG genotype of the VDR (FokI) gene polymorphism compared to those with the AA and AG genotypes. No relevant medical studies on bone health were identified. Conclusion. This study confirms a significant decrease in BMD in children with asthma compared to those in medical settings and reveals significant changes in biochemical markers of bone metabolism. Low vitamin D levels and limited physical activity in this group of patients necessitate comprehensive treatment and correction of metabolic changes to prevent long-term complications, including osteoporosis. A multidisciplinary approach that combines stress management, nutritional status improvement, and physical activity is essential to BMD and reduce the risk of bone disease in adulthood.

The newborn screening program (NBS) plays a critical role in the development of the healthcare system of the Russian Federation. Since 2023, the Order No. 274n “On the approval of the Procedure for providing medical care to patients with congenital and/or hereditary diseases” has extended the scope of neonatal screening. The expanded newborn screening (ENS) includes detection of 36 nosological conditions. Among these, inborn errors of immunity (IEI) represent a significant and still extending group of genetic disorders characterized by increased susceptibility to infections due to underlying immunopathological mechanisms. At the initial stage, quantitative determination of T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) is performed for all newborns in order to identify individuals at risk and initiate confirmatory diagnostics. This approach enables the detection of IEI before the onset of clinical symptoms. This article presents and analyzes the results of ENS program for IEI conducted at the Northwestern Federal District (NWFD) during the period from 2023 to 2024. Over this two-year period, a total of 209,741 newborns were screened at the NWFD. Among them, 818 newborns (0.39% of those screened) were classified as high-risk IEI cases. The immunodeficiency states were identified for 45 children as based on immunophenotyping of peripheral blood lymphocytes (IFT), and genetic causes of the condition were confirmed in 49% of these cases. Statistical analysis revealed associations between gestational age and birth weight with TREC levels, and, to lesser extent, with KREC levels. The reference intervals were established for defined subgroups of neonates. These findings highlight the importance of continuous observation of newborns classified as moderate-risk cases. Notably, 9% of all screened individuals were designated as “conditionally healthy,” despite having TREC or KREC values below the lower reference limit. Based on the obtained data, the models for optimizing the screening program for IEI were proposed. These findings contribute to earlier diagnosis and more effective management of patients with immune disorders, as well as enhanced personalization of therapeutic strategies. Establishing population-based reference intervals plays a key role in standardizing methods for diagnostics and monitoring the immune system, thus representing an important step in overall advances of healthcare.

Hereditary neuromuscular disorders (NMDs) comprise a clinically and genetically heterogeneous group of conditions characterized by the involvement of the peripheral nervous system and skeletal muscles. This work presents a literature review focusing on brain neuroimaging findings in hereditary NMDs detected by magnetic resonance imaging. The aim of this work was to describe and synthesize current data on brain magnetic resonance imaging abnormalities across various hereditary NMDs, based on a literature review and a clinical case series, and to evaluate potential clinico-radiological correlations. A literature search was conducted in the PubMed database from 1984 to 2025 July using keywords including (white matter lesion) AND (myotonic dystrophy), (white matter lesion) AND (hereditary neuropathy), (white matter lesion) AND (Charcot–Marie–Tooth), (white matter lesion) AND (muscular dystrophy), (white matter lesion) AND (myasthenic syndrome), and (white matter lesion) AND (motor neuron disease). A total of 107 publications were included in the final review. A clinical case series with magnetic resonance imaging data is also presented, including Charcot–Marie–Tooth disease type 1X, myotonic dystrophy types 1 and 2, merosin-deficient congenital muscular dystrophy, and limb-girdle muscular dystrophy type 23. The reviewed literature indicates that brain magnetic resonance imaging can have both diagnostic and prognostic clinical significance in some hereditary NMDs, especially in myotonic dystrophies, merosin-deficient muscular dystrophy, and Charcot–Marie–Tooth disease type 1X. The presented case series illustrates the variety of magnetic resonance imaging patterns and their association with clinical manifestations, underscoring the importance of integrating neuroimaging into the diagnostic workup for hereditary NMDs.

Primary immune regulatory disorders (PIRDs) are a group of conditions characterised by a loss of immune tolerance. Two such disorders, CHAI and LATAIE, share common molecular mechanisms, leading to significant clinical overlap. Here, we report demographic, clinical, immunological, and molecular findings in 29 patients referred from different parts of India with a diagnosis of CHAI or LATAIE. LATAIE patients demonstrated a higher prevalence of consanguinity, while CHAI patients more often had a positive family history. Both disorders presented with overlapping clinical features, predominately autoimmune cytopenias, benign lymphoproliferation, and inflammatory bowel disease (IBD). However, the incidence of recurrent infections, otitis media, bronchiectasis, and hypogammaglobulinemia was higher among LATAIE patients as compared to CHAI. Flow cytometry analysis revealed significant differences in T cell subsets, particularly in percentages of CD4+ naïve cells and T regulatory cells (Treg), between the two disorders. B cell abnormalities were also observed. Molecular diagnosis was achieved using targeted or clinical exome sequencing, and specific protein expression was employed to validate the novel variants.

Background/Objectives: Comprehensive genomic profiling (CGP) is a cornerstone of personalized oncology. However, large-scale, systematic data on the somatic mutation spectrum in Russian cancer patients are scarce. This study aimed to characterize the genomic landscape and assess the potential for matched therapy in a Russian cohort of patients with solid tumors. Methods: This retrospective study included 204 patients with various solid tumors. CGP was performed using the FoundationOne®CDx (FFPE tissue) and FoundationOne®Liquid CDx (cfDNA) platforms. The analysis assessed single-nucleotide variants, indels, copy number alterations, gene fusions, tumor mutational burden (TMB), microsatellite instability (MSI), and PD-L1 expression. Results: The most frequently mutated genes were TP53 (61.5%) and KRAS. The median TMB was 4.0 mut/Mb and was significantly lower in stage IV tumors. Significant co-occurrence was observed between KRAS and TP53 mutations, as well as between APC and KRAS mutations, which were particularly characteristic of colorectal cancer. KRAS mutations were associated with higher combined positive score (CPS) values in cases with lung cancer. Based on the CGP results, 44% of patients had findings that supported the use of an approved matched targeted therapy or immunotherapy for their tumor type. An additional 36% of patients had alterations indicating potential benefit from off-label targeted therapy. Conclusions: This study reveals the distinct genomic characteristics of solid tumors in a Russian cohort and confirms the high clinical utility of CGP for identifying actionable targets. Implementing CGP early in the diagnostic process is a necessary step towards realizing personalized treatment strategies for cancer patients.

Relevance. Modern research in the field of biomedicine leads to the development of therapeutic drugs based on extracellular vesicles, which are defined as sources of production, as well as targeted modification. In the presented work, for the first time, transcriptome profiling of primary culture of cortical neurons under the influence of extracellular vesicles obtained from glial cells during glutamate excitotoxicity was carried out in order to determine differentially expressed genes. Materials and Methods. Extracellular vesicles were obtained from the conditioned medium of human glial progenitor cells using ultracentrifugation. Model of glutamate excitotoxicity, distributed on the first cultured cortical neurons of cells (P0) with the addition of 100 μM glutamate. Sequencing of prepared libraries of electronic technologies on the NextSeq 1000 platform (Illumina, USA) using the NextSeq 1000/2000 P2 (200 cycles) v3 reagent kit supplemented with 2 % Phix (Illumina) as an internal control. The criterion for statistical innovation of gene expression change between officially recognized FDR 0.05. Results and Discussion. Transcriptome analysis showed that the addition of extracellular vesicles during glutamate excitotoxicity leads to increased expression of 190 genes and decreased expression of 309 genes (p value 0.05 and |FC| 1.5). Gene analysis using the Gene Onthology database showed that genes with increased expression are consistently classified by biological processes. The most represented were: regeneration, reorganization of the extracellular matrix and cytoskeleton, maintenance of homeostasis, activation of the PI3K-Akt pathway and response to cellular stress. Genes with reduced expression were consistently classified into groups: calcium transport, regulation of neuronal processes, apoptosis, glutathergic synapse. These data can indicate that. Extracellular vesicles trigger survival processes in nerve cells when exposed to glutamate and inhibit pathways associated with the entry of substances and glutamate into the cell. Conclusions. Extracellular vesicles enhance the expression of genes with survival and inhibit genes, resulting in calcium transport and apoptosis. The results of the study show the promise of using extracellular vesicles of glial origin as a basis for developing new therapeutic approaches to individual neurological diseases.